He then returned to Israel to teach at the Hebrew University as a lecturer in the Faculty of Law and Department of Philosophy. In 1971, he was tenured and promoted to Senior Lecturer. In 1972, he returned to Balliol as a Fellow and Tutor in Law, becoming a Professor of Philosophy of Law, Oxford University, from 1985 to 2006, and then a Research Professor from 2006 to 2009. Since 2002 he has also been a Professor in the Law School at Columbia University, New York. Raz, now retired from Oxford, is currently also a visiting professor of law at King's College London.[1]

A pupil of H. L. A. Hart, Raz has been important in continuing the development of legal positivism both before and since Hart's death. Raz was also co-editor of a second edition of Hart's The Concept of Law with a postscript including Hart's responses to other philosophers' criticisms of his work.

Raz's first book, The Concept of a Legal System, was based on his doctoral thesis. A later book, The Morality of Freedom won two prizes: the 1987 W.J.M. Mackenzie Book Prize from the Political Studies Association of the United Kingdom, awarded to the best book in political science each calendar year; and the 1988 Elaine and David Spitz Book Prize from the Conference for the Study of Political Thought, New York, awarded annually for the best book in liberal and/or democratic theory that had been published two years earlier. The book develops a conception of perfectionist liberalism.

Raz has argued for a distinctive understanding of legal commands as exclusionary reasons for action and for the "service conception" of authority, according to which those subject to an authority "can benefit by its decisions only if they can establish their existence and content in ways which do not depend on raising the very same issues which the authority is there to settle."[2] This, in turn, supports Raz's argument for legal positivism, in particular "the sources thesis," "the idea that an adequate test for the existence and content of law must be based only on social facts, and not on moral arguments.".[2]

Raz is acknowledged by his contemporaries as being one of the most important living legal philosophers. He has authored and edited eleven books to date, namely The Concept of a Legal System (1970), Practical Reason and Norms (1975), The Authority of Law (1979), The Morality of Freedom (1986), Authority (1990), Ethics in the Public Domain (1994), Engaging Reason (1999), Value, Respect and Attachment (2001), The Practice of Value (2003), Between Authority and Interpretation (2009), and From Normativity to Responsibility (2011). His most recent work deals less with legal theory and more with political philosophy and practical reasoning. In moral theory, Raz defends value pluralism and the idea that various values are incommensurable.